JTC has also rented out space in the other two levels to tech start-ups. It has 27 tenants, of which eight are tech incubators.
Block 71, which has more than 100 tech start-ups altogether, is the flag bearer for Singapore's start-up effort and has become a must-stop destination for any visiting tech investor and entrepreneur.
It has a vibrant community where entrepreneurs, investors and programmers rub shoulders.
Many networking, pitching and other events are held there each week.
Observers note that if the current tenants who have created this vibrant community move to other parts of the island, they will take with them their experience of building new companies, which will not benefit the newbies coming in.
Tenants enjoy low rents of as little as $1.60 per sq foot, according to some, although MDA declined to reveal its rates.
Tenant and entrepreneur Darius Cheung said: "Rental is one of the most expensive costs in Singapore. Most start-ups take five to seven years to mature and be financially independent.
"For a three-year-old start-up to pay commercial rent, it would definitely prematurely increase its burden of building a company," he said.
Mr Cheung, who founded his third start-up, homie.co, a local apartment and room search portal, added: "What MDA is trying to do is like forcing a heart transplant onto the start-up ecosystem at Block 71 when it is still growing up."
Tenants received notice of the lease expiration last week but they can stay until September next year as MDA has extended their tenures by six months. MDA also held a dialogue with tenants last week. Mr Vincent Lau, co-founder of social commerce platform Paywhere, said MDA told tenants that it was not breaking up the start-up community.
"Although they have given us the letters, things may still change. They understand that having start-ups at different stages will help entrepreneurs become more successful," he added.
In a statement to The Straits Times, MDA said existing tenants have to make way for new start- ups so that these can enjoy the low rents as well as access to mentorship and expertise. It wants to ensure a healthy renewal of start-ups at Block 71, it added.